75 



construction of gas apparatus, would, however, be attended 

 with great inconvenience and expense, and moreover, would 

 not avert other dangers incident to the disruptive discharge 

 from the conductor to the gas and water pipes within a 

 building. I have therefore recommended that in all cases 

 where lightning conductors are attached to buildings, fitted 

 up with gas and water pipes, the lower extremity of the 

 lightning conductor should be bound in good metallic con- 

 tact with one or other of such pipes outside the building. 

 By attending to this precaution the disruptive discharge 

 between the lightning conductor and the gas and water 

 pipes is -prevented, and the fusible metal pipes in the 

 interior of the building are placed out of t]ie influence of 

 the lightning discharge. 



Objections have been raised by some corporations to the 

 establishment of metallic connexion between lightning con- 

 ductors and gas mains, on the ground that damage might 

 arise from ignition and explosion. These objections are most 

 irrational, as gas will not ignite and explode unless mixed 

 with atmospheric air, and the passage of lightning along- 

 continuous metallic conductors, will not ignite gas even 

 when mixed with air. Moreover, in every case of the ignition 

 of gas by lightning, the discharge is actually transmitted 

 along the mains, such objections notwithstanding. A gi-ave 

 responsibility therefore rests upon those, who, after intro- 

 ducing a source of danger into a building, raise obstacles 

 to the adoption of measures for averting this danger. 



Dr. Joule remarked that, at 20 minute past 4, when the 

 hail storm was at its height, the atmosphere was illuminated 



